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Q&A: Ceiling Cracks With Trusses

Slab-on-Slab

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A.Jim Vogt, P.E., responds: According to the best available data, roof truss movement occurs in a very small number (approximately 20%) of reported cases of partition separation. This movement is typically caused by differences in the moisture content between the top and bottom chords of the truss. Other potential causes of partition separation include:

Preventive action during construction is the best way to avoid costly repair work. Properly balanced attic ventilation helps prevent partition separation by exhausting moisture from the air in the attic space. Continuous eaves and ridge ventilation is most effective. When appropriate, "floating corners" should also be used to minimize the...